This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT Bronchopulmonary dysplasia (BPD) of prematurity has emerged as the most common, lethal and expensive neonatal pulmonary disorder in the United States. The pathogenesis of BPD is multi-factorial, has a genetic contribution, and involves injury and inflammation associated with oxygen toxicity and mechanical ventilation in an underdeveloped, immature lung. The estimated prevalence is 30,000 cases/year. Current therapeutic approaches to the prevention and treatment of lung disease in premature infants, including antenatal corticosteroid treatment, replacement surfactant at birth, postnatal administration of corticosteroids, vitamin A, diuretics, caffeine, and bronchodilators have not significantly impacted the overall occurrence of BPD. Recent clinical trials of inhaled nitric oxide (iNO) indicate a beneficial impact on the incidence and severity of BPD as well as short- and long-term safety including 2-year neurodevelopmental outcome. Extremely low birth weight infants (ELBW, defined as 1 week of age. Aim 2. Assess effects of late surfactant treatment on the respiratory status of ventilated ELBW infants. We will collect clinical data to investigate effects of surfactant treatment on both short-term respiratory support need, as assessed by the Respiratory Severity Score (RSS), and pulmonary status at 36 weeks PMA (survival without BPD). We also will monitor for evidence of toxicity as indicated by any of the known complications of surfactant administration as well as by the occurrence and severity of other common morbidities of preterm infants, including intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL), patent ductus arteriosus (PDA), necrotizing enterocolitis (NEC) and retinopathy of prematurity (ROP). We expect that combined iNO-surfactant therapy will be safe. We will determine the relationship between surfactant function (Aim 1) and both short-term respiratory status and 36-week outcome.